Paul Horton, the experienced batsman, will leave Lancashire at the end of the season after the club did not offer him a new contract.
Horton revealed he had begun discussions with the club over his future earlier in the season and said he had wanted "to look at his options". He was overlooked for the captaincy when Tom Smith was named as Glen Chapple's successor while Steven Croft was named vice-captain.
Horton made his debut for Lancashire in 2003 and was the leading run-scorer when they won the Championship in 2011. Last season he also captained them to the final of the T20 Blast.
He has been a regular in the first team this season, playing all 12 Championship matches to date in which he has scored 611 runs at 35.94, but has not played in all the limited-overs cricket.
"I have had a wonderful time at Lancashire. From my first game as a 15-year-old to all 308 competitive professional games for the club," Horton said. "The pinnacle has to be helping Lancashire win the County Championship in 2011, especially after 77 years of waiting. It was also an honour and privilege to captain the side to the NatWest T20 final last year.
"After speaking to the club in mid-season, I wanted to have a look at my options and I am now looking forward to a fresh challenge where my experience can hopefully benefit a new club. I wish the club every success in the future."
Director of cricket Ashley Giles said: "Paul has been a tremendous servant to Lancashire and has been a key member of the squad during my time at Old Trafford. This was a tough decision to make and I would like to thank Paul for all of his efforts for the club. We all wish him well in the future."